Rheostat.



PATENTED AUG. 16, 1904..

1. B. SMITH.

RHEOSTAT.

APPLICATION FILED DBO. s, 1903.

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No. 767,916. PATENTED AUG. 16, 1904. I. B. SMITH.

RHEOSTAT.

APPLICATION FILED DEC. 3, 1903. 110' MODEL. 2 SHEETS-SHEET 2 Snow 1, 506

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' 2y /JLM' M +22 (180141013 Patented August 16, 1904.

IRVING B. SMITH, OF PHILADELPHIA, PENNSYLVANIA.-

RHEOSTAT.

SPECIFICATION forming part of Letters Patent N 0. 767,916, dated August 16, 1904.

Application filed December 3, 1903. Serial No. 183,640- (No model.)

To all whom it may concern.-

Be it known that I, IRVING B. SMITH, acitizen of the United States, residing at Philadelphia, in the county of Philadelphia and State of Pennsylvania, have invented new and useful Improvements in Rheostats, of which the following is a specification.

The principal objects of this invention are to secure in rheostat construction economy, simplicity, and general efiiciency characterized especially by an increased capacity to dissipate and radiate the'heat generated in the resistance material.

'ith the above ends in view my said invention relates to the manner of winding and sup portingthe resistance material on the rheosta't, whereby all portions of said material are made equally effective in dissipating the heat produced therein and whereby all portions of said material are intimately associated with heat-dissipating and heat-radiating bodies to the end that there shall be but a small drop in heat potential from the heat-producing resistance to the final heat-dissipating surface.

My invention consists also in the construction or formation of the switch-contact segments and the simple means for affixing them to their supporting-base, their relation with respect to the resistance 'material, and the means for forming electrical connection between the said resistance material and the said contact-segments.

My invention consists, further, in the combination and arrangement of parts hereinafter more fully described, and particularly pointed out in the claims.

Referring to the accompanying drawings, which illustrate an embodiment of my said invention, Figure 1 represents a top plan view of the rheostat; Fig. 2, a vertical section, partly in side elevation; Fig. 3, a side elevation of the rheostat with the outer casing removed to show a step in the construction; Fig. 4, an enlarged detail perspective view of one of the switch-contacts, showing the method of connecting the resistance material thereto; Fig. 5, a bottom plan view of'said switchcontact; Fig. 6, an enlarged vertical sectional view of one side of the rheostat; and Fig. 7, a section along the line a; :0, Fig. 4, looking in the direction of the arrows.

In the accompanying drawings, 1 represents a slate or other suitable insulating plate or base upon which is carried the stationary switch-contacts. These contacts are of peculiar construction and, as above pointed out, constitute an important part of this invention. They consist each of a piece of sheet metal stamped out and bent upon itself, so as to form a switch-contact segment 2, a heel 3, and strip extensions 4, the latter forming substantially a right angle with said contact portion 2, as shown most clearly in Fig. 4. The switch-contacts 2 are held in position on the upper face of the base 1 by the lips 5 and 6, punched out of the strip of which the contact is made, the lip 5 engaging a small hole 7 in the upper face of the plate 1, and the lip 6 engages the under edge of said plate, as shown most clearly in Fig. 6. This manner of connecting the said contacts to the plate is simple and eiiicient and eliminates the use of attaching-screws. The lip 5 prevents the contact-segment from slipping in a horizontal plane, while the lip 6 clamps the segment securely against the base.

The switch-arm 8 is of common construction, consisting of a resilient metal strip mounted in the usual manner upon a stud 9 in the center of the contact-base. The stud 9- is electrically connected by conductor 10 with a suitable binding-post or terminal contact 11. The other binding-post or terminal contact, 12, is connected after the usual manner to the last contact-segment 2 of the series.

The contact-base l of the rheostat is supported upon metal brackets or supports 13, secured to the under side thereof by countersunk bolts 14. These brackets have extensions 15, which are bent outward from the under side of said contact-base, and these extensions are secured to the inside of a metal annulus or ring 16, having around its lower edge a flange 17.

The strip extensions 4 of the switch-contacts extend over the outer periphery of the ring 16 and are separated therefrom by the insulation 18, which preferably covers the outer surface of said ring, extending slightly above the upper edge thereof.

The disposition of the resistance-con;luctor and the manner of connecting the same to 'in the process of winding.

the contact-segments constitute another important part of my invention, as hereinbefore pointed out, and is essentially new in rheostat construction. According to this invention the resistance-conductor, which is preferably a bare wire or ribbon, although it may be either.

insulated or what is called ship-wound where the conductor is only partly covered, is wound in a continuous spiral over the insulated extensions of the switch-contact segments arranged around the periphery of the ring, and electrical connection between the said resistance-conductor and the proper segments is effected by carrying the conductor between the upper and lower strip extensions of the contact-segment with which it is desired to make electrical connection. This construction is shown most clearly in Figs. 3, 4, and 6, where 19 represents the resistance-conductor wound over strips of mica 20 or other suitable insulation upon the upper face of the strips 4:. In winding the resistance-conductor on the rheostat one end thereof is connected to one of the strips a say at the point 21 (see Fig. 3)by passing the said conductor between the upper and lower members of said strips, where the short end of the conductor may be bent over the top of the strip to prevent it from being pulled out of place The resistanceconductor is then wound over the insulated tops of said extensions 4: until enough has been wound to form the first step of resistance, when the said conductor is passed between the next pair of strip extensions 4:, with which it makes electrical contact in the manner above described, and so on around the rheostat until all of the said strips are electrically connected to the resistance-conductor at points throughout its "length to form the required resistance-steps. The winding of the resistance-conductor over the said extensions after placing the said conductor under ,the top member of such extensions binds the said conductor mechanically at such point and insures good electrical connection. This construction also eliminates all breaks in the resistance material and renders soldering unnecessary. Moreover, the distribution of the resistance-conductor in this manner over the metal strips, which are in turn in close proximity to the metal ring, will effect a most liberal dissipation or radiation of heat.

The resistance-conductor is preferably covered by insulation 22, over which is placed. a metal casing 23, which further increases the relatively largeheat-radiating surface of the rheostat.

The contactsegments are further held against the base 1 by a flanged collar 24:, which encircles the extension of said contacts just below the heel portion 3.

A stop 25 upon the upper face of the base 1 limits the rotation of the switch.

The rheostat may be secured to a switchboard or other suitable support by attachingscrews or their equivalents passed through the slots 26 in the ends of the brackets 13.

Having thus described a form of my invention which is susceptible to considerable modification without departing from the spirit thereof, what I claim is 1. In a rheostat, the combination with a switch-base, of a plurality of switch-contact segments mounted on said base and provided each with an extension, and resistance material wound substantially normal to said extensions and electrically connected thereto atintervals.

2. In a rheostat, the combination with a switch-base, of a plurality of switch-contact segments mounted on said base and provided each with an extension, continuous resistance material wound substantially normal to said extensionsand electrically connected thereto at intervals.

3. In a rheostat, the combination with a switch-base, of a plurality of switch-contact segments mounted on said base and provided each with an extension substantially normal to the plane of the switch-contact surface of said segments. and resistance material wound upon said extensions in a direction substantially normal thereto and electrically connected at intervals to said extensions.

4. In a rheostat, the combination with a switch-base, of a plurality of switch-contact segments mounted thereon and provided each with extensions, resistance material wound about said extensions collectively and brought between extensions of a given segment to form electrical connection therewith in establishing a resistance-step.

5. In a rheostat, the combination with a switch-base, of a plurality of switch-contact segments mounted thereon and provided each with extensions, an insulated metal surface upon which said extensions are arranged, and resistance material wound about the said extensions collectively and insulated therefrom except at determinate points, the said material being electrically connected at such points to said extensions individually to form the resistance-steps.

6.-In a rheostat, the combination with a switch-base, of a plurality of switch-contact segments wound thereon and provided with extensions, of an insulated metal surface upon which said extensions are arranged, resistance material wound about the said extensions collectively and insulated therefrom except at determinate points, the said material being electrically connected at said points to said extensions individually to form the resistancesteps, and a metal covering over said resistance material and insulated therefrom.

7 In a rheostat,'the combination with a switch-base, of a plurality of switch-contact segments wound thereon and provided each with extensions substantially normal to the plane of the switch-contact surface of said IIO segments and disposed around the edge of said base, a metal annulus or ring around which the extensions of said segments are arranged, and resistance material wound about said extensions and brought between the extensions of a given contact-segment to form electrical connection therewith in establishing the resistance-steps.

8. In a rheostat, the combination with a switch-base, of a plurality of switch-contact segments wound thereon and provided each with extensions substantially normal to the segments and disposed around the edge of said base, a metal annulus or ring'around which the extensions of said segments are arranged, resistance material wound about said extensions and brought between the extensions of a given contact-segment to form electrical connection therewith in establishing the resistance-steps, and a metal casing around said resistance material and insulated therefrom.

9. In a rheostat, the combination with a switch-base, of a plurality of switch-contact segments mounted thereon and provided each with extensions consisting of superimposed strips of conducting material extending in a direction substantially normal to the face of said base and disposed around the edge thereof, a metal annulus or ring around which said extensions are arranged, means for securing said annulus to said base, continuous resistance material wound about said extensions collectively and brought between the superimposed strips of given extensions to form electrical connection with the said segments in establishing the resistance-steps, and a metal casing inclosing said resistance material and insulated therefrom.

10. In a rheostat, the combination with a switch-base, of a metal ring or annulus secured thereto, a plurality of pairs of superimposed metallic strips arranged around and insulated from the periphery of said ring, bent at their ends to extend partly over the face of said base to form switch-contact segments, resistance material wound over and plane of the switch-contact surface of said insulated except at intervals from said strips and brought between respective pairs of superimposed strips to form electrical contact in establishing the resistance-steps, means for securing said strips to said base, and a metal casing inclosing said resistance material and insulated therefrom.

11. In a rheostat, a switch-contact segment consisting of a strip of metal bent upon itself to form a flat switch-contact portion and extensions substantially normal to said portion.

12. In a rheostat, a switch-contact segment consisting of a strip of metal bent upon itself to form a flat switch-contact portion and extensions substantially normal to said portion, and retaining-lips stamped out of said strip.

In testimony whereof I have signed my name to this specification in the presence of two subscribing witnesses.

IRVING B. SMITH.

WVitnesses:

WM. 0. HOWELL, LINDA Corn SMITH. 

